Work gripping conveyor for assembling apparatus and methods



Jan. 18, 1966 S. J. GARTNER WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS Original Filed Jan. 29, 1954 7 Sheets-Sheet l INVENTOR. STANLEY J. GARTNER ATTORNEYS Jan. 18, 1966 5. J. GARTNER 3,229,801

WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS Original Filed Jan. 29, 1954 "r Sheets-Sheet 2 INVENTOR STANLEY J. GARTNER BY M%W ATTORNEYS Jan. 18, 1966 5. J. GARTNER WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS '7 Sheets-Sheet 4 Original Filed Jan. 29, 1954 INVENTOR.

STANLEY J. GARTNER ATTORNEYS Jan. 18, 1966 5. J. GARTNER WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS 7 Sheets-Sheet 5 Original Filed Jan. 29, 1954 INVENTOR. STANLEY J. GARTNER ATTORNEYS Jan. 18, 1966 5. J. GARTNER WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS 7 Sheets-Sheet 6 Original Filed Jan. 29, 1954 u R E BY Mh ATTORNEYS Jan. 18, 1966 5. J. GARTNER 3,229,801

WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS Original Filed Jan. 29, 1954 7 Sheets-Sheet 7 STANLEY J. GARTNER ATTORNEYS V United States Patent "ice 3,229,801 WORK GRIPPING CONVEYOR FOR ASSEMBLING APPARATUS AND METHODS Stanley J. Gartner, Emporium, Pa., assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application Feb. 7, 1962, Ser. N0. 171,745, which is a division of application Ser. No. 406,930, Jan. 29, 1954, now Patent No. 3,069,749, dated Dec. 25, 1962. Divided and this application Sept. 19, 1963, Ser. No.

This application is a division of application Serial No. 171,745 filed February 7, 1962, which is a division of application Serial No. 406,930, now US. Patent No. 3,069,749 of December 25, 1962.

The present invention relates generally to work gripping conveyors used in connection with methods and apparatus for automatically assembling parts, particularly the component parts of a mount or electrode assembly of an electronic tube or the like.

During the several decades of technical development and commercial exploitation of vacuum tubes and the like there has been a persistent need for improved methods of assembly and for automatic assembling apparatus for the electrodes of such devices. Some early machines were devised that were adapted to assemble simple types of mounts but even these were unsuccessful to my knowledge.

For many years, tubes have included many electrodes, and with the development of the hearing aid and the proximity fuze, the dimensions of many types of tubes have been greatly reduced. It will be recognized that as mounts are made progressively smaller, manual assembly without deforming the delicate electrodes becomes progressively more difficult. In the event that a mount is assembled imperfectly, perhaps including a deformed electrode, the defective nature of the mount may not be detected until after the mount is sealed in its envelope as finally exhausted and completed. At this stage, it is revealed as defective after it represents a far greater expenditure than is represented by the mount itself. In other words, manual assembly techniques tend to deform the electrodes in such a way that defective mounts are often detected after the tube construction has advanced to an expensive stage. The methods and apparatus provided by the present invention vastly reduce this tendency to deform electrodes; and any deformation produced occasionally is so prominent as to be immediately detected and the mount can be rejected while still representing comparatively small cost.

It is accordingly an important object of the present invention to provide new and improved methods and apparatus for automatically assembling electronic tube mounts and the like. A further object is to automatically assemble electrodes of even small and complicated mounts in rapid precise and automatic routine.

The machine includes a conveyor which carries a number of work holders from each of a series of stations to the next, step-wise. Because of the small dimensions of the illustrative mount being assembled and the consequent close tolerances involved, it is important that the conveyor should consistently advance the work holders to an accurate position in each station. Ordinary conveyor mechanisms, such as the usual chain conveyor, tend to introduce slack and in this way tend to defeat the objective of accurate transport of the work holders. A feature of this invention resides in a conveyor having unusually large links, and correspondingly, having relatively few links. A subsidiary feature relates to the conveyor that is disposed about a pair of sprockets, one of 6 Claims.

3,229,801 Patented Jan. 18, 1966 which is movable to and from the other so as to accommodate the travel of the large links about those sprockets. The use of an odd number of links minimizes the motion of the movable sprocket, and the consequent impacts on the frame and in the drive are minimized.

In the illustrative machine, the previously molded glass-and-wire stems are loaded manually onto a conveyor plate with rough preliminary orientation. A feature of the invention resides in the techniques and mechanisms for handling the glass-an-d-wire stern during its transfer from the initial feed plate to the work holders of the main conveyor, so as to preserve and improve the initial orientation and to effect this transfer in a simple manner well suited to specialized forms of stems.

Further features of novelty will be appreciated from the illustrative disclosure that follows. It will naturally be understood that certain aspects and features of the described embodiment may be omitted as required and that certain features are useful in other combinations. However, the entire organization is admirably adapted to achieve the broad purpose of assembling and uniting the electrodes of a mount, particularly in assembling numerous electrodes of a subminiature mount. In the detailed disclosure, reference is made to the accompanying drawings forming part of the present disclosure. In the drawings:

FIGS. 1A and 1B are a plan view of an illustrative mount machine embodying features of the present invention, including the work conveyor and portions of the coordinating drive and cam mechanisms of the various work stations, showing in greatly enlarged perspective the progress of a typical mount during passage through the several work stations of the machine but omitting those stations;

FIG. 2 is an elevation in cross-section along the line 22 of FIG. 1 but at larger scale, showing the jawopening mechanisms for the stem blocks or work holders and the drive mechanism of the several stations of the machines;

FIG. 2A is a portion of FIG. 1A at larger scale showing details of the link conveyor for the stem block and the guide mechanisms for maintaining the stem block along a predetermined path during travel through successive stations;

FIG. 3 is an enlarged fragmentary elevation, with parts broken away and sectioned, showing the details of the work holder or stem block;

FIG. 4 is a sectional view taken substantially along the line 44 of FIG. 3 and looking in the direction of the arrows;

FIG. 5 is a perspective view, with parts broken away, of the stem block illustrated in FIGS. 3 and 4;

FIG. 6 is an elevation, certain parts sectioned and broken away, showing portions of the mechanism of FIG. 1A together with the stem-loading mechanism at Station A of FIG. 1A;

FIG. 7 is an enlarged fragmentary elevation, viewed generally from the line 77 of FIG. 6 and looking in the direction of the arrows, showing the turret indexing mechanism;

FIG. 8 is an elevation, with some parts broken away and shown in section, taken substantially along the line 88 of FIG. 6 and looking in the direction of the arrows, showing the details of transfer fingers for displacing successive stems from the feed turret onto a two part trans fer member;

FIG. 8A is an elevation showing the details of a split funnel guide interposed between the transfer member and the stem block in FIG. 6;

FIG. 9 is a perspective view showing the details of the two part transfer member of FIG. 6 with a stem loaded therein ready for transfer;

- FIG-.40 is a four stage progressive illustration of the transfer member of FIG. 6 is successive positions of movement from receiving a stem at the feed turret to delivering the stem through the split guide to the stem block;

FIG. 10A is an enlarged fragmentary plan view showing a stern on the feed turret together with part of the transfer member, as viewed just prior to the first diagrammatic showing of FIG. 10;

FIG. 11 is a timing chart of the conveyor and stem block operating mechanism shown in the preceding figures, wherein the time-motion curve is generally identified by the same numerals as are used for the cams producing such timed motions;

FIG. 12 is a timing chart of the mechanism in the stem loading station.

In FIGS. 1A and 1B there is shown the plan view of a conveyor 12 and associated operating mechanisms for assembling a number of electrodes to a stem made up of wires sealed in a glass header h. The assembly of the electrodes and the stem is termed a mount in the art. Such an assembly may be of various sizes, and the principles here involved will be recognized as applicable to a wide range of designs of mounts and the like. However, the present machine is particularly adapted, by the solution of numerous special problems, to the assembly of mounts of extremely small proportions. The tube used in this illustrative embodiment is a pentode having a twopart anode, a wire or rod suppressor, a screen grid, and a control grid, all of which extend parallel to the length of the tube and are fixed in relative spacing each from the others by an insulating wafer at each end of the electrode assemblies, usually of mica. The particular tube is intended to receive a filamentary cathode that is manually added to the mount after the mount is delivered by this assembling machine. The diameter of the tube being fabricated is the so-called T-3 size, that is, approximately outside diameter of the glass enclosing envelope.

The tube is assembled by commencing with a stem or header that is loaded into a conveyor and is transported step-wise past a series of operating stations A to L inclusive where the header wires are either shaped by cutting and swaging or where one or more of the electrodes and the micas are assembled or welded to produce the completed mount. The extremely small dimensions of the mount being assembled represent a controlling consideration throughout the machine. Thus, the machine itself forms certain of the mount parts in accurate configuration so that the part will be in perfect orientation for assembling and so that, when the sub-assembly leaving one station reaches a succeeding station, the various parts of the sub-assembly will be in accurate position and relative arrangement for the operation at the succeeding station.

In FIG; 1A three stations, A, B, and C are seen where a stem block 10 on the linked conveyor 12 comes to rest successively. At the first station A, glass header h having sealed wires 1 to 9 inclusive, is mechanically loaded on the conveyor in proper position for the further operations in the succeeding stations B and C. Wires 1, 2, 3, 4, 8, 9, extend from the wafer header h in particular positions appropriate for succeeding operations which are effected at further stations during the travel of the conveyor between the stem-loading and unloading positions A and L.

By loading the stem into the machine with the wires 1 .to 9 inclusive of equal length and longer than the longest wire needed, it becomes possible to trim the wires to lengths required during further assembly operations, all accurately in relation to a common reference, namely, the wafer header h. In the first part of the conveyors traverse, there is seen a mount completed by this machine. This includes a bottom mica hm spaced accurately from the header h. The locationof the bottom mica 4 bm is established partly by the wires 2, 8 and 9 cut short and having their ends defining a plane against which the bottom mica is pressed. Additionally, leads 1 and 4 (which extend through the bottom mica bnt for connection to the two anode plates) have swaged abutments at the plane of cut leads 2, 8 and 9 for supporting the bottom mica bm.

By loading an uncut and unswaged stern into the stem loading station A, it becomes possible to cut certain leads to critical lengths at a further station, and at a still further station to swage accurately located shoulders on certain leads, thereby defining the bottom mica plane. This may be accomplished with the assurance that, although the trimming and swaging are effected at different stations, the operations are consistently related to each other by the accurate orientation of the stem at each of the stations, both as to the end-wise positioning of the wire and as to the wire pattern presented at each station to the operating tools.

Wires 6 and 7 ultimately serve as suppressor electrodes, and are also utilized to support and connect thefilamentary cathode. At the cutting or trimming station B, leads 6 and 7 remain uncut and are of the same full length as when received in the stem loading station A; but two other sets of leads are trimmed to different lengths, specifically leads 2, 8, and 9, are trimmed to very short lengths equal to the spacing between the glass header h and the bottom mica bm, and leads 1, 3, 4, and 5 disposed in an approximately square pattern, are trimmed to a medium length such as to penetrate the bottom mica bm and extend part way toward the top mica tm.

In station C, two of the medium length leads namely 1 and 4, are swaged to provide a shoulder or abutment at the same separation from the header h as the ends of wires 2, 8, and 9. The position of the swaged shoulders S and the cut ends of the wires 2, 8, 9 are all of a high order of accuracy because of the accurate grip of header h in a stem holder and the holder is located precisely at each station in the machine. It is an important feature that the header h is seated in its holder and is maintained in a very definite fixed plane in its traverse through the machine from station to station, and further that each of the wires, 1 to 9 inclusive, remains in a very accurately established position endwire and transversely. It will be seen that in some of the stations the accuracy of the positioning of these wires and their pattern is reestablished and carefully readjusted.

It will be understood that the header h as formed in a stem molding machine carries the wires 1 to 9 in a pattern whose accuracy and consistency is limited, considering the requirement of stem molding dies that the wires should be loosely received; and because automatic assembling of a mount must not be impeded by variations in the pattern or distribution of the wires, stations A, B and C of the present machines are adapted to receive wire patterns of coarse tolerance and adjust the pattern of wires to close tolerance, before other parts are assembled.

In station D, the bottom mica bm is applied to wires 6 and 7 and pushed part Way down the lengths of these wires but not to the final position where it is pierced by medium length wires 1, 3, 4 and 5 and rests against the ends of short wires 2, 8 and 9, and the swaged shoulders S of the wires 1 and 4.

At the bottom mica-applying station D (see FIG. 1B) an important principle of the machine is utilized further and again illustrated. The accurately oriented wires whose positions are fixed in the stem-loading station A and adjusted in both the cutting and swaging stations B and C are to receive a bottom mica having a pattern of holes. The machine itself forms the holes immediately prior to application of the bottom mica to the wires. Thus the holes which are to be penetrated by the uncut reference wires 6 and 7 are in the proper positions and relative spacing to assure that the bottom mica bm can be mechanically thrust against the Wire ends, in alignment with the corresponding holes. The remainder of the holes are accurately distributed to receive the medium length wires 1, 3, 4 and 5 that were correspondingly accurately adjusted in the previous stations B and C. These wires penetrate mica bm at a later station when mica bm is pressed against stops provided by the ends of short leads 2, 8, and 9.

At this station D a further mechanism is included for shifting the short wires to definite positions, when necessary, so that such wires will assuredly not obstruct the side rods of grids that are later inserted.

In the next station E (with the bottom mica bm supported in its intermediate position along the uncut reference wires 6 and 7) a grid g1 is inserted into two of the holes of the bottom mica which are properly located for receiving the grid side rods. This is effected by accurate orientation of the wires 6 and 7, which act in turn to carry the pierced bottom mica into accurate position for receiving those side rods. Since the bottom mica bm is perforated in the machine, specifically at the station D, no precaution is required to prevent inversion of the hole pattern such as might occur if the bottom mica were formed separately and subsequently loaded into this assembling machine. Thereafter, at station E, a metal sleeve, or grid stop gs is formed in the machine and applied to the end of a side rod of grid g1 that projeots through the bottom mica, to hold the grid g1 firmly against the bottom mica bm. This grid stop is welded to one of the side rods of the grid g1 at the underside of the bottom mica bm. The sleeve gs is extremely tiny, when it is borne in mind that the bottom mica bm is of the order of A in diameter. The grid stop is not handled as a separate part but is cut, formed, applied, and welded, entirely within station E. The spacing provided between header h and the bottom mica bm in its preliminary position facilitates the assembling and welding operations. Later, when the bottom mica bm is advanced to its final position, there is little clearance for application of welding tools.

The other side rod of grid g1, extending through the bottom mica bm, ultimately is disposed close to short wire 9 which terminates at the lower face of the bottom mica bm; and in a welding step expediently effected manually, that side rod is joined to wire 9 which constitutes the lead conductor for the #1 grid in the finished, sealed tube.

At the next station F, a second grid g2 is mounted coaxially of and around g1 and the side rods of the grid g2 are forced through the accurately located holes in bottom mica bm; and then the subassembly of grids g1 and g2 and bottom mica are advanced to their final position with the bottom mica in the assembly plane defined by short wires 2, 8 and 9, and abutting against the swaged portions S of medium length leads 1 and 4.

In the grid-applying stations E and F the bottom mica bm is in its intermediate position during the insertion of each of the grids g1 and g2. After the grids have been inserted, the bottom mica bin is finally seated. In the next following stations G and H two portions of a two-part anode may be successively thrust into position on opposite sides of the grids g1, g2 and against the accurately located bottom mica. The two-part anode includes a front part a on leads 3 and 4, and a second part a on leads 1 and 5.

In station I a top mica tm is pierced and applied to the long wires 6 and 7 as was the bottom mica km in station D. In the following stations I and K, wire straps or hairpins are formed and inserted for interconnecting the two parts a of the anode, and to hold the top mica tm in place against the top edges of the anode parts. Finally, in the station L of the machine, the excessively long, previously uncut reference wires 6 and 7 are trimmed to a desired length, and the assembled mount is unloaded from the machine.

A further principle will be seen, applied repeatedly. in

various stations of the machine. In loading the stem into the stem blocks at the station A, the relatively fixed pattern of wires at the locations where they emerge from header h is used as a reference. In stations B and C where the wires are cut and swaged, and in the other stations where the uncut or long wires and electrode side rods are held, the possibility exists that any of those long wires or the electrode side rods may be deflected from the reliable pattern defined by the wires closely adjacent the header and/ or by the bottom and top micas bm and tm. In stations B, C, and D, the long and slender wires extend to unreliable positions at their free ends. The apparatus engages the wires close to the header Where the wire pattern may be relied on, and a combing pattern of tool apertures is formed and then moved perpendicularly away from the header h to the position where the cutting die, the swaging die, or the mica-applying head is to engage the previously unsupported and unreliably positioned wire ends. These cutting, swaging and assembling tools then advance along the wires toward the header in a reverse stroke, to reach their final working positions.

The novel step-wise conveyor shown in FIGS. 1A and 1B should be properly appreciated, since it is very important to the operation of the mechanism at the several work stations from the stem loading station A to the final trimming and unloading station L. In one respect it might be ideal if the several stern blocks 10 which hold the individual stems at spaces equal to the spaces between the various work stations were part of one rigid disc, or turret. In that event, their relative spacings might conceivably be rigidly and invariably fixed. The location of the work mechanisms would then require most remarkable precision, and thermal dimension changes would require special accommodation. In contrast, stem blocks 10 are carried by a link conveyor in the machine described, in a semifloating condition so that they can be accurately located in each station by mechanism at that station, and to use a linked conveyor, sprocket-supported at its opposite extremities. This concept is applied in my copending application Ser. No. 790,570, filed Dec. 9, 1947. It is of special advantage that a minimum number of strong large links should be used. This minimizes stretching of the links and minimizes the total effects on the conveyor of the looseness and wear at individual pivots, contrasting in this respect from conventional chain conveyors.

Where large links are used, that are wrapped around a pair of spaced drive and guide sprockets, provision should be made for the sprocket shafts to move toward and away from each other as each large link approaches a sprocket, swings around the sprocket, and then leaves. This motion should be minimized to avoid excessive stresses on the conveyor with resulting unreliable positioning of the work holders in the work stations. This sprocket motion is minimized by using an odd number of large links, to insure the presence of one link at only one sprocket, that extends across the line of the two sprocket shafts, while at the opposite sprocket a pair of links form a V-configuration. This condition of a fiat link at one end and V links at the other changes as the conveyor advances with this V first at one sprocket and then at the other. The arrangement promotes smooth conveyor operation. Because of the large size of the individual links, one of the sprockets is mounted with a yielding bearing permitting sliding movement toward and away from the opposite fixed-shaft sprocket. If a flat link were to pass around a sprocket at one end and a corresponding flat link were to pass around a sprocket at the opposite end, followed by the V-joint between the two links being disposed at one end of the conveyor and a corresponding V-joint at the opposite sprocket, then the yieldably supported sprocket would bounce excessively, perhaps to a damaging degree. Also, vibrations would be produced operation as is here involved.

Accordingly, conveyor 12 is made of an odd number of links, forty-five in the present case, each third link 12a bearing a stem block 10. There are twelve work stations in the machine, with one stem block at each station and with three additional stem blocks in transit around the end sprockets 14 and 16. The end sprocket 16 has a suitable bearing 17 that is horizontally slidable to and from the end sprocket 14, and is spring biased away from sprocket 14, for tensioning the conveyor 12. The conveyor 12 advances stepwise around bed 11. A main drive shaft 18 driven from a motor (not shown) is provided which furnishes power to a suitable intermittent rotary drive transmission 13 (see FIG. 1) effective for indexing sprocket 14 180 at a time followed by idle intervals. A specially desirable form of such intermittent drive transmission 13 for the machine is disclosed in my copending application Ser. No. 294,902 filed June 21, 1952. Since sprocket 14 has six radial sprocket teeth spaced one conveyor link apart, the conveyor advances threelinks, identified with one stem block, for each ad- Vance of sprocket 14. Main drive shaft 18 is geared to continuously rotate horizontal cam shaft 20 continuously and thereby operate a series of control cams to be described, and main drive shaft 18 is also coupled via gearing 22 to rotate a series of vertical drive shafts for furnishing continuous synchronised rotary power for shafts 23 at the various work stations spaced along the conveyor.

Sprocket 14 has a pair of pins 24 which are engaged by a locking detent 26 (see FIG. 1A) for arresting and locating the conveyor in the intervals when the various stem blocks are disposed opposite the several work stations. During sprocket indexing motions, detent 26 is withdrawn by a linkage 28 of any convenient design operated by a cam 30 on continuously rotating cam shaft 20.

The drive mechanism in FIGS. 1A and 1B includes a further pair of earns 32 on cam shaft 20 (see FIG. 2) for rocking levers 34 which, through segmental gears 34a and pinions, 36a, cause rock shafts 36 to oscillate. These rock shafts extend along all the work stations, Their purpose is to operate the clamping mechanisms, to be described, for arresting and accurately locating the stem blocks 12 in the several work stations. Additionally, continuously rotating cam shaft 20 furnishes power for mechanically opening the various stem blocks 12 at certain times in the sequence of operations. For this purpose, cam shaft 20 carries a series of cams 38 which, through mechanism that includes cam followers 40 operate jaw opening wedges. The two cam followers 40 seen to the left in FIG. 1A are seen to operate through crank shafts 40' to actuate the jaw openers in the loading and unloading stations A and L. The cams shown in FIG. 1A appear in end projection n FIG. 2, together with an end projection of the locatmg and jaw-opening mechanism for the stem blocks at the respective stations. As seen in FIG. 2, each cam follower 34 at each station, caused to oscillate by a constrained cam 82 on the common cam shaft 20, operates a segmental gear 34a which in turn oscillates pinions 36a (see also FIGS. 1A and IE) on rock shaft 36 in bracket 35'. A separate pinion 36b is fixed to the shaft 36 at each work station, and operates through a segmental gear 37 and link 36d to oscillate a lever 36e and a rock shaft 36' in the direction opposite rock shaft 36. Fixed to each of the common rock shafts 36 at both sides of the ma-.

chine, as shown in FIG. 2, is a series of arms 36f, one for each work station, and also fixed to rock shafts 36' is a further series of arms 36g. Pivotally supported on shafts 36 and 36' are additional arms 36h and 36i, respectively. Arms 36 and 3612 at the respective stations are urged apart by coil spring 36i, while arms 36g and 36i are urged apart by coil springs 36k. The several sets of arms 36)- 36h, and 36g-36i are held together by bolts 36m. Accordingly, as the respective arms 36 are oscillated counter-clockwise (at the left of FIG. 2) by rock shaft 36, the associated arms 36h are yieldably carried along. Similarly, .as arms 36g are oscillated clockwise (at the left of FIG. 2) by rock shaft 36, arms 36i are yieldably carried along. Arms 3611 at the respective stations are seen to have lateral extensions engaging vertical slides 3611, each supporting a single pin 360, while arms 361' are seen to have extensions engaging slides 36p each supporting a vertically reciprocating pair of pins 36g. These pins are shown also in FIG. 3. Each of the slides 36p carries a stop 36s engaging an adjustable screw stop 361' fixed in the machine frame so as to limit the upward stroke of the slide 36p.

The single pin 360 and the pair of pins 36g reciprocate oppositely, as a pair of jaws, for seizing the stern block 10 at times when the conveyor 12 brings successive stem blocks opposite these pins and for locking the stem block in place while the conveyor remains at rest. Pins 36g raise the stem block yieldably to a fixed limit. Pin 360 yieldably drives the stem block in the opposite direction.

As the cam followers 34 rock shafts 36 and 36' to oscillate the mechanisms described, springs 36] .and 36k transmit the oscillatory thrust to the pin 360 and the pins 36: which seize each stem block, However, at each station, spring 36k is deliberately made substantially stronger than spring 36i and for this reason the upward stroke of the pin set 36g is more foreceful than the downward stroke of pin 360. Accordingly, the level at which each stern block 10 is finally positioned is determined by the adjustment of screw 36r. The downward stroke of pins 360 is adequate to grip the stern blocks, but not so forceful as to depress pins 36q.

The foregoing mechanism will be seen to be the mechanical analogue of the pneumatic conveyer-block gripping mechanism disclosed in my copending application, Serial No. 790,570 filed December 9, 1947.

FIG. 2 shows the constrained cams 38 and the cam followers 40 which were previously described for the purpose of operating the stem block jaws Ni, 10 for seizing and releasing the stems. Specifically, cam followers 40 are seen to have arms 40a for driving opposed slides 40b outwardly. These slides carrying wedges 400 which engage the stem block jaws and periodically separate the jaws at times and in stations where necessary, as will be described in detail below. The stem block jaws are opened to receive a stem in the stem-loading station A and to release the completed stem in the stem-unloading station L. Additionally, the stem block jaws are quickly opened and closed in each of the two work stations immediately following the stem loading station, namely the lead trimming and swaging stations B and C. It will be understood that all of the cam shafts, drive shafts and slides described have bearings in frames 11 and 35, details of which need not be described.

The links of conveyor 12 carrying the stem blocks 10 are shown in detail in FIGS. 2 and 2A. Link 12a bearing a stem block 10 carries roller 12b and rollers 12d disposed respectively behind and in front of rail 12c. The rollers 12b and 12d cooperate with the rail 126 to guide the chain conveyor along an accurate path through the machine. A further fixed frame plate 12e overlies rearwardly projecting plates 12e' on links 12a for preventing the links from tipping. Each of the stem-block supporting links 12a has an outwardly projecting bracket 12 for the block 10, Rollers 12d cooperate with the sprockets, while each roller 12b is received between the sprocket arms.

The operation of the mechanism described to this point will be readily understood. Main drive shaft 20 rotates continuously to drive sprocket 14 intermittently at a time. Sprocket 16 is driven by the chain conveyor, and supports and yieldably tensions the chain conveyor 12. Looking detent 26 is reciprocated in timed relationship to the indexing operation of sprocket 14 for arresting the conveyor in accurate indexed positions and for precluding movement of the drive sprocket 14 between indexing operations. Rock shafts 36 raise the respective single pins 360 and rock shafts 36' lower the respective sets of pins 364; for releasing the stem blocks 10 during indexing and operate reversely for gripping the blocks 19 when the chain conveyor 12 comes to rest. Adjustable stops 361', with the effect of unequal springs 36k and 36 determine the elevation of the stem block 10 when it is locked in position. At an appropriate time in the operating cycle of the machine, while the stem blocks 10 are gripped by cooperating pins 360 and 3661, cam followers 40 operate wedges 40c to open the stem-block jaws, the details of which are described below. The links 12:: of the chain conveyor 12 which carry the stem blocks 10 are accurately guided along the path fixed by rail 12c and the cooperating rollers 12b, 12d.

The stem blocks 10, briefly described in connection with FIGS. 2 and 2A, are shown in greater detail in FIGS. 3, 4, and 5. Each stem block 10 is suspended on the outwardly extending brackets 12 of the supporting conveyorlink 12a by pins 10a extending through enlarged bores in the bracket 12 one pin appearing at each side of the stem block 10. Springs 10b surround pins 10a and bias the body 10c downward as limited by pins 10d. Body 10c is formed with respective channeled and conical recesses 10e providing bearing seats for the gripping pins 360 and 36q. Pin 360, in its conical seat 100, centers the block from left to right as viewed in FIG. 3. Body 10c has a central insert 10 constituting a seat for the glass header h, the insert 10] being formed with a passage 10g for receiving the projecting wires extending from header [1. In addition, a pair of passages 10/2 on opposite sides of the insert 10 admit jaw opening Wedges 400 when projected by the cam mechanisms 40, 40a and 4% previously described.

The body 10c slidably supports a pair of vertically movable jaws 10i and 10 disposed in front of insert 10 for pressing header h against the insert and for gripping and centering the header h. A pair of plates 10k are fixed to the body 10c for slidably confining the jaws ltli and 10 As seen in FIG. 5, each side of upper jaw lfii has a lateral extension 10m that lies behind a similar lateral extension 1012 on lower jaw 10 The upper and lower jaws 10i and 10 are urged toward each other by a pair of inwardly spring biased wedges 100 each of which has a compression coil spring 10p. Wedges 100 coact with sloping faces 1011' of side notches in the lateral extensions 14in of the lower jaw 10j and with sloping faces 10m of side notches in lateral extensions 10m of the upper jaw 19L Inward pressure by compression springs 10p forces wedges 100 to concurently raise the lower jaw 19 and depress the upper jaw 10], to firmly grip the header h. The jaws force the header h firmly against seat provided by the insert 10 by virtue of sloping header-engaging surfaces 101 of the jaws.

Jaws 101 and 10 have reversely sloping cam surfaces ltlr and 10s (see FIG. 5) in their rear surfaces engaged by wedges 49c when it is necessary to open these jaws.

From the foregoing, it is seen that the stern blocks are relatively loosely suspended from brackets 12 of the conveyor 12 and accordingly the conveyor 12 is only relied upon to transport the stern blocks 10 to successive positions to a first degree of accuracy. Thereafter, gripping and locating pins 36 and 360 accurately fix the location of the stem blocks 10 after the conveyor 12 has come to rest. Between those brief intervals when wedges separate jaws 101' and 10 spring biased wedges 100 urge jaws 101' and 10] toward each other for resiliently gripping and centering the header h and for firmly seating the header. The headers are gripped at all times, both when the con veyor 12 is advancing and when it is at rest, except in the four stations A, B, C and L as previously mentioned. By

virtue of the stem-block gripping mechanism, which accurately locates the stem-block 10 in each of the work stations, and the further header-gripping mechanism in the stem-block, the stem is successively positioned in the several work stations to a high degree of accuracy with front-to-rear and rotational orientation preserved continuously after it is once perfected.

The timing of the drive and indexing mechanisms, utilized in the various stations to be described, is represented in FIG. 11. Sprocket 14 is intermittently advanced by any suitable continuous-to-intermittent drive means 13, illustrated in FIG. 11 to complete the conveyor advance in the interval 35 to Gradual acceleration and deceleration, together with rapid operation, is to be desired. Cam 3@, which operates conveyor detent 26, advances the detent into the path of the next pin 24 after the pin previously released has been carried part way around with the sprocket. Firm locking of the sprocket by cam 30 and detent 26 is effected after conveyor drive has ceased.

Cams 32 operate the stem-block gripping pins 360 and 36: to seize and release the stem-block at the beginning of each cycle of operation of the tools on the stems in the respective stations, blocks 10 being locked in place as early as practicable and being released as late as practicable. This is indicated by the timing curve 32 in FIG. 11 corresponding to the drive effected by cam 32 in FIGS. 1A and 2.

Cams 38 operate wedges 40 to release the stems in stations B, C, and L, and to open the stem holders arriving in station A. Each station requires its own cam 38 and its own timing curve 38 represented, in FIG. 11, as will be appreciated when considering the various stations A, B, C and L specifically.

A feature of the invention reperesented by the mechanism in station A involves the location of a part in a preliminary orientation followed in later stations by successive refinements in the preliminary orientation. This assures reliable performance of the assembly machine despite inaccuracies or loose tolerances in the dimensions and in the distribution of the parts involved.

An important consideration in assembling the electrodes on the stem h having the series of wires 1 to 9 inclusive molded in a predetermined pattern involves the accommodation of stems in which the highly flexible wires are in a predetermined arbitary pattern. The wires may not be distributed in a precise predetermined pattern, due to a certain degree of required looseness of the wires when received in passages in the molding dies where the stem was formed. Much more serious is the fact or random deformation of the comparatively long and slender wires incidental to handling. After loading of stems, the machine corrects wire deformity.

The details of station A are shown in FIGS. 6, 7, 8, 8A, 9, l0 and 10A, wherein there is illustrated mechanisms for initially loading a stem into the stem block 10 previously described. The loader not only inserts a stem into the stem block 10, but additionally predetermines the orientation of the wires 1 to 9 inclusive in relation to the stem block 10. There is no critical physical dimension which is utilized in the stem block 10 to predetermine the rotatonal orientation of the stem in the stem block, but instead, the stern loader itself is relied upon to insert the stem with particular wires in positions required for functioning of succeeding work station. Thus wires 6 and 7, considered as reference wires, are to be disposed one above the other in a vertical plane while the wires and the axis of the stem are horizontal. These conditions are obtained while the glass header is seated against the insert 10f in the stem block 10. Wire 7 is disposed above wire 6, and the remaining wires are distributed in the initial pattern determined by the glass molding operation. In station A, the stems are manually deposited on the blades of a feed plate turret, with no more than rough orientation required of the attendant.

. l I From this point, the mechanism performs automatically with progressively increasing precision in stem handling and in stem-wire tailoring, including straightening, cutting, pattern-adjustment and swaging of the wires.

In FIG. 6 the general organization of the stem-1oading station A is shown, the mechanism for operating certain parts being shown in FIG. 8. The stem loading mechanism includes a step-wise advanced carrier or turret 41, a set of transfer fingers 42, a pair of transfer arms 44 and 45, a split-funnel wire guide 46, and the necessary operating mechanisms coordinated as shown in the cam )chart of FIG. 12. In FIG. A there is shown a holder 41a of the carrier 41 having a blade 41b extending between reference wires 6 and 7 arranged on one side, and wires 1, 2 and 3 on the other side. Blade 41b is approximately the maximum thickness permitted by the separation of these two groups of wires and so may be said to be tightly confined or wedged between them. Whether tight or loose, the stem rests on the edge of its blade and is prevented from tipping radially on the turret by the length of the blade engaged by the glass of the stem and is further prevented from tipping across the blade edge by the width of the blade engaged by the wires. Blade 41b penetrates the extending array of wires and serves to initially determine the rotational position about the stem axis in which the stem is ultimately loaded into the stem block 10.

The stems h are loaded manually or by appropriate automatic mechanisms onto the respective holders 41a, conveniently at the extreme left of turret 41 as seen in FIG. 6, and from this position the stems are indexed in the clock-wise direction, when looking down on the turret. As the turret 41 indexes, the stems are carried into a transfer position between transfer fingers 42 and the adjacent stem block 10 on the conveyor 12.

Turret 41 is supported on an upright shaft 410 journaled in a fixed bearing 41d. Supported on the lower face of turret 41 is a series of cam followers 41a which (see also FIG. 7) cooperate with a constrained barrel cam 41 having an integral medial rib 41g filling the space between two successive cam followers 412. The rib 41g locks the turret 41 during part of the cam rotation. Additionally, barrel cam 41 has two curved runs 40h for producing the desired cam indexing motion. Barrel cam 41 rotates in a fixed bearing 411' (see FIG. 6) and is driven by a sprocket and chain drive including a sprocket 41 a sprocket 41m, and a chain 41k trained over the sprockets. The sprocket 41m is on a secondary drive shaft 4111 driven through bevel gearing from unit drive shaft 41p, the latter being coupled, as described above, to the main drive shaft of the machine. A suitable single-revolution electromagnet-controlled clutch 23a is interposed in the main drive shaft connection of this unit to the main drive of the whole machine, for control by appropriate manual or automatic devices, and a like clutch is included in the drive connection of each of the other units driven by shaft 20. Turret 41 carries a stern h into range of transfer fingers 42 for each revolution of the main drive 20.

The purpose of transfer fingers 42 is to shift the particular stem on a blade 4112 on to an aligned blade 44a of the transfer arm 44. Transfer fingers 42, seen best in FIG. 8 (as viewed looking toward a stem block with turret 41 removed) are swingably supported on one end of a lever 42a having a central pivot 42b and a cam follower 420 on its opposite end. The lever 42a is biased by spring 42d against upstanding edge cam 42e on the shaft 4121.

When turret 41 has carried a stem to the transfer position in front of the horizontally extending transfer fingers 42, and when transfer arms 44, 45 are in their vertical position with the blade 44a aligned with and bearing against the blade 41b (FIG. 10A), the transfer fingers 42 are operated by cam 42e to displace the stem from the turret carrier 41a to the transfer arms 44, 45. The transfer fingers 42 follow the transfer arms 44, 45 arcuately toward the stem block 10 to provide the requisite sup port, but are quickly returned to the position shown in FIG. 6 prior to or during the next indexing of the turret 41. Accordingly, after the turret indexes one step, the next stem will be disposed in the transfer position in front of transfer fingers 42.

The transfer fingers 42 and their supporting lever 42a, cam follower 42c and operating cam 42e are shown best in FIG. 8 wherein there is illustrated an additional novel feature. A test or detecting finger 42 is carried on an insulating block 42g to move with transfer fingers 42. In the event that no stem is present on a carrier 41a for transfer operation to a particular stern block, then an electric circuit is conditioned appropriately to suppress operation of the further assembly mechanisms in succeeding stations which would otherwise operate on the stem carried by the particular stern block during the processing cycle. The suppression of operation of the further stations in respect to the empty stem block is effective in saving parts which cannot be assembled for lack of a stem in the stem block. Delayed control (Serial No. 790,570) disables clutches 23a.

A split-funnel wire guide 46 and associated operating mechanism, shown partially in FIG. 6, are more completely illustrated in FIGS. 8 and 8A. The guide 46 includes two pivoted arms each having a funneled or flared portion 460 in the face 46a closest to the transfer arms 44, 45. Each arm has a smaller generally cylindrical portion 460 reaching face 46b (FIG. 6) facing stem block 10. The guide or funnel 46c is split and formed on the separate arms of the guide which swing reversely with pivoted pinions 46d and 46e. The pinion 46:: is engaged by a segmental gear 46 spring-biased to close the split funnel. Normally the funnel arms are spread apart to provide a clear passage between transfer arms 44, 45 and the stem block 10. Segmental gear 46 is positively driven downward through link 46g coupled to bell crank lever 46h. Bell crank lever 46h, pivoted intermediate its ends and rocked counter clockwise by link 461', is coupled to a further bell crank lever 46 carrying cam follower 46k engaging edge cam 46m on the shaft 41p that is geared to shaft 41n. connected to bell crank 46f, biases the linkage between segmental gear 46 and the cam follower 46k in the reverse direction. Cam 46m opens split guide funnel 46 at all times except during actual insertion of the forwardly projecting wires into the hollow stem block insert 10f.

The transfer arms 44 and 45, Which receive the stems from turret carrier 41a, are effective to swing the stems from a vertical stem-receiving position to a horizontal stem-inserting position, whereupon the stem wires are thrust endwise into the hollow insert 10 of the stem block 10, via split funnel 46. The transfer arms 44, 45 are shown greatly enlarged in FIG. 9, and their operating mechanisms appear in FIGS. 6 and 8. The transfer arm 44 has a pivot 43a journaled on a carriage 44b, the latter being horizontally slidable along a horizontal pair of guide rods 44c. The carriage 44b is biased by spring 44d toward the stem block 10, that is, in the direction of inserting a stem into the stem block 10. The carriage 44b is positively driven away from the stern block 10 by a lever Me and cam follower 44 engaging cam 44g on shaft 41m. Lever 44a and cam follower 44] are interconnected by a long shaft 44h (FIG. 8) mounted for oscillation in fixed bearings.

As seen in FIG. 9 the transfer arm 44 has a rearward extension 441' which is capable of swinging clockwise under action of torsion spring 44 to engage a stop 44k on carriage 44b. The cooperating extension 44i and the stop 44k accurately arrest the transfer arm 44 in the horizontal stem-inserting position. The transfer arm 44 has a cam follower 44n bearing against stationary cam 44m. Arm 44 is raised from the horizontal when carriage 44 Spring 46q moves away from the stem block 10. When the transfer arm 44 and the integral cam follower 44n are carried with carriage 44b to the right and toward the stem block 10, transfer arm 44 is swung clockwise intov horizontal stem-inserting position. This is shown in progressive stages in the first three diagrams of FIG. 10. It is seen that transfer fingers 42 push the header 41b or stem 11 from the turret 41 and its supporting blade 41b to the transfer arms 44, 45. In the first part of FIG. 10, fixed cam 44m engages rearwardly extending cam follower 4411 to maintain transfer arm 44 in the vertical stem-receiving position.

As carriage 44b moves to the right in FIGS. 6 and 10, cam follower 44n gradually slides off the stationary cam and spring 44 urges the transfer arm 44 clockwise and into the horizontal stem-inserting position with extension 44: against abutment 44k.

Transfer arm 45 is carried by pivot 45a in transfer arm 44 and biased against transfer arm 44 by a torsion spring 45b, so that the two arms may move as a unit, horizontally and arcuately as shown in the first three phases of FIG. 10. Transfer arm 45 has an integral rearwardly extending cam follower 450 whose function will be clear from the following.

The purpose of transfer arm 45 becomes apparent from the third and fourth views of FIG. 10 where the stern h is seen to extend horizontally. In the event that the transfer arm 45 were omitted, there would be considerable danger that, despite the frictional engagement of the wires with blade 44a, the stem still might shift or fall from the single transfer arm 44. By the time the extending wires on the stem h enter and pass through the split-guide funnel 46, the transfer arm 45 has served its intended purpose. As carriage 44b continues its horizontal travel to the right in FIG. 10 cam follower 45c, comes into engagement with a fixed cam 45d. The transfer arm 45 is thereby swung to an inoperative position of clearance, seen in the last diagram of FIG. 10. With the transfer arm 45 out of the way, the transfer arm 44 with its supported stem approaches the split guide funnel 46. After the funnel 46 has guided the leads into the stem block 10, the funnel, too, is removed and transfer arm 44 is effective to complete the insertion of the stem into stem block 10. Thereafter, jaws 101, 10 of the stem block 10 are closed by proper coordination of the jaw-opening wedges 40c previously described. When the stem block jaws 101', 10 have siezed the glass header of the stem, carriage 44b slides horizontally to the left in FIGS. 6 and 10, thereby withdrawing the transfer arms 44, 45 from the projecting stem wires.

The wires extending through the insert 10 of the stern block 10 ultimately will constitute the external terminals of the completed selection tube, while the wires projecting from the front face of the stem block 10 will be variously processed and used in the assembly of the mount, as will appear.

In review, preliminary orientation of the stems to be located into stem block 10 is effected with the aid of blades 41b projecting radially from turret 40 during loading of the stems onto the holders 41a. By the cooperative effects of transfer fingers 42, transfer arm 44 with its transfer blade 44a, and transfer arm 45, this orientation is maintained as the stem is inserted into stern block 10. The leads that project from the face of the stem block 10 are thus disposed in the pattern required for operations at further stations. The glass 'header is pressed by stem block jaws 101' and 10 with their sloping edges against the seat provided by block insert 10 The timing of certain cam-operated mechanism in station A is represented in FIG. 12. There it is seen that cam 44g operates carriage 44b carrying transfer arms 44, 45 to the left (FIG. 6) and to upright position near the start of the cycle. Thereafter transfer fingers 42 are advanced to bear against a stem and push it from plate 41 to arms 44 and 45. Split funnel 46m closes in front of a. stem block that had just been carried to station A by the conveyor, as represented by the drop in curve 46m. Arms 44 and 45 start to travel toward the stem block near. the ZOO-degree point in the cycle (curve 44g) and cam 42e continues to swing fingers 42 with arms 44 and 45 until those arms approach the horizontal. Carriage 44b advances arms 44 and 45 further toward the stem block while jaws 46 are closed, but near the end of travel of those arms jaws 46 open and the stem is seated in the stern block.

Cam 38 which operates the stem block jaws in station A should have a drop shortly after the conveyor comes to rest, and should have a rise while cam 44g has its dwell (305 to 320 in FIG. 12) so that the inserted stem is seized before arm 44 is withdrawn.

While one stem is being loaded into the stem block as described, arm 42 is swung to the extreme left by cam 42a, and feed plate indexing cam 41 advances the feed plate 41 one step to bring the next stem in front of fingers 42. Arms 44 and 45 then return in readiness for the next machine cycle.

The glass header may vary in diameter and in thickness, but the self-centering characterisics of the stemblock jaws, and the sloping surfaces of the jaws that engage the glass are effective to accommodate wide variations in glass dimensions.

When the stem block reaches station L, the mount is complete, very nearly in the form delivered in the assembling machine. It is a rigid unit, with the electrodes, the micas and the stem accurately and permanently united. Several operations must still be done before this mount can be enclosed in its envelope, namely the grids are to be joined to stem wires and a cathode is to be inserted and connected in place. With other forms of electrode and mounts, the concepts in the foreging disclosure can readily be adapted to fabricate a technically complete mount. In the present machine, the long wires #6 and #7 are to be cut shorter, and the mount is to be withdawn from the stem block. The stem wires #6 and #7 were deliberately made longer than required in the finished stern, for their functional contribution in the asseembling process. In station L, a mechanical pair of cutters trims those wires, and a pair of jaws appropriately formed are provided to grip and withdraw the mount from stem block 10. As seen in FIGS. 1A, 2 and 5 one of the camoperated stem block mechanisms 30, 40 previously described releases the amount for unloading. In the event of misoperation resulting in a mount remaining in a stern block after leaving station L, an operator can still clear the stem block during the next machine cycle and before the stem block enters the loading station A.

The mechanism of station L is not separately illustrated and described in detail because its nature will be clear from the foregoing description to those skilled in the art.

The various features of the invention are believed amply shown and described to the extent that recapitulation might serve to confuse rather than to clarify. It should be noted that the total result of the operation of the properly adjusted apparatus is represented in the integral mount delivered which is of such excellence that rejection of a finished tube because of an electrode assembly defect is rare. This is a prominent advantage of the mechanically assembled mount over a manually assembled product.

The organized apparatus may be modified in innumerable respects. For example, the conveyor 12, while of unique construction adapted to the machine disclosed, might be dispensed with entirely in an evasive effort, and in its place manual attendants might physically move stem blocks 10 from each assembly unit to the next. Furthermore, in assembling like products of modified designs, portions of the assembling apparatus and method may be omitted or adapted to meet requirements. Consequently the appended claims should be broadly construed, consistent with the spirit and scope of the invention.

What I claim is:

1. A work processing machine including a stepwise conveyor, a work holder carried loosely by said conveyor and including a pair of jaws biased toward each other, a workholder gripping mechanism at a work station for seizing and locating said work holder, and a jaw-opening mechanism operable in time with said conveyor and said workholder gripping mechanism and including means for spreading the jaws while the work holder is at rest.

2. A work processing machine including a stepwise conveyor, a work holder carried loosely by said conveyor and including a pair of jaws biased toward each other, a

work-holder gripping mechanism at a work station for seizing and locating said work holder, and a jaw-opening mechanism operable in time with said conveyor and said work-holder gripping mechanism and including means for spreading the jaws while the work holder is at rest, said Work-holder including a seat and said jaws including surfaces diverging in the direction of said seat effective to seize an inserted object and bias the object against the seat.

3. In a multiple station machine, a conveyor, means for advancing said conveyor intermittently, a work holder carried by the conveyor and including a pair of confronting jaws mounted for movement toward and away from each other, means operative to normally urge said jaws toward each other, reversely sloping camming surfaces on adjacent portions of said jaws, and jaw-opening mechanism operable in time with the conveyor advancing means and While the work holder is at rest and including a Wedge movable relative to said jaws and engaging said camming surface-s for concurrently spreading said jaws.

4. A multiple station machine according to claim 3 wherein the means operative to urge said jaws toward each other includes reversely sloping camming surfaces on adjacent portions of said jaws, and a spring-biased wedge engaging said latter camming surfaces.

5. In a multiple station machine, a work holder including 'a pair of confronting jaws mounted for movement toward and away from each other, rear-slanting edges on said jaws for gripping a work piece, reversely sloping camming surfaces on opposed portions of said jaws, thrust means bearing against said camming surfaces and biasing said jaws toward each other, and jaw-opening mechanism including a wedge directed between opposed jaw portions for periodically exerting a spreading force between said aws.

6. A conveyor including a holder having work-gripping jaws, means at certain locations along the conveyor path and coacting with said jaws to open same, said jaws having slide hearings in said holder, paired reversely sloping cam surfaces on lateral surfaces of said jaws, and a pair of spring biased guided wedges thrust in opposite directions against the respective reversely sloping cam surfaces and effective to bias said jaws toward each other and to center the gripped work automatically.

References Cited by the Examiner UNITED STATES PATENTS 868,741 10/1907 Wendt 198-179 X 1,533,710 4/1925 Sproul 269-57 2,401,000 5/1946 Kucyn 26957 3,116,821 1/1964 Davis 19819 3,119,486 1/1964 Davis 19819 SAMUEL F. COLEMAN, Primary Examiner.

RICHARD H. EAMES, JR, EDWARD A. SROKA,

Examiners. 

1. A WORK PROCESSING MACHINE INCLUDING A STEPWISE CONVEYOR, A WORK HOLDER CARRIED LOOSELY BY SAID CONVEYOR AND INCLUDING A PAIR OF JAWS BIASED TOWARD EACH OTHER, A WORKHOLDER GRIPPING MECHANISM AT A WORK STATION FOR SEIZING AND LOCATING SAID WORK HOLDER, AND A JAW-OPENING MECHANISM OPERABLE IN TIME WITH SAID CONVEYOR AND SAID WORKHOLDER GRIPPING MECHANISM AT A WORK STATION FOR SEIZING SPREADING THE JAWS WHILE THE WORK HOLDER IS AT REST. 